Clingman's Dome is the highest peak in Tennessee. It rises in the Great Smoky Mountain National Park, and is the most frequently visited of all United States highpoints, hosting nearly ten million people annually. The trail to the summit is a short hike up a paved trail from the parking lot. A wheelchair-accessible observation tower, built in 1959, marks the summit, towering above the forest and providing occasionally breathtaking vistas. The beauty of this once spectacular spot has deteriorated significantly, due to a combination of heavy automotive traffic on the mountain, industrial air pollution throughout the region, and an aphid infestation that is rapidly wiping out the fir trees.